1. Field of the Invention
This invention pertains generally to optical instruments, and more particularly to drift corrected optical instruments.
2. Description of Related Art
Conventional dual-trap optical tweezers employ two laser beams, one of which (at least) is steered by a device such as a piezoelectric mirror or acousto-optic modulator. Each beam is focused by a microscope objective to trap two microspheres tethered by a molecule of interest and the displacements of the beads are monitored to follow the dynamics of the system being studied.
One critical problem currently limiting the performance of high-resolution optical traps is that the mechanical drift of optical components often results in physical drift in the location of an optical trap that is larger than the detected displacement-of-interest. The motion of biological motor proteins that are specific to interacting with DNA often take steps along the double helix that is on the order of 0.3 nm in size, and so accurate measurements of this small motion requires that drift of the trap positions be smaller than this value. However, the current best-performing optical traps suffer from instrumental drift that is almost twice what can be tolerated, and at least a substantial source of this noise is mechanical drift in optical components that are required for beam steering.
The precision of conventional optical tweezers relies on the passive stability of the instrument itself, and therefore demands costly engineering solutions aimed at controlling environmental noise that can be coupled into the optical components and result in mechanical drift of the traps. This results in costly engineering solutions to limiting environmental noise in the optical mounts, such as optical tables and basement laboratories for vibration isolation and temperature control. Consequently, high-resolution measurements are not currently possible in laboratory settings that lack the resources (e.g. vibration isolation and temperature stability) to implement these strict conditions.